The present invention relates to a high speed pickling device and a method therefor, and in particular, relates to a high speed pickling device and a method therefor which removes in a short time oxidized scales formed on the surfaces of a thin plate during thin plate hot rolling.
Conventionally, removal of the oxidized scales on the surfaces of the thin plate after hot rolling was performed in such a manner that the thin plate was allowed to cool in the air to an ordinary temperature and was caused to travel in acid fluid such as hydrochloric acid and sulfuric acid having a concentration of 10-15% and at a temperature of 80.degree. C. to thereby remove the oxidized scales through pickling as disclosed in JP-A-61-41783 (1986). Pads were provided so as to sandwich a thin plate at the top and bottom thereof, and by causing the thin plate to pass through a narrow passageway formed of the opposing wall surfaces of these pads, thin acid fluid layers of turbulent flow were formed by partially cutting boundary layers formed on the surfaces of the traveling thin plate thereby pickling the surfaces of the thin plate with these acid fluid layers. Further, in the pickling device the narrow passageway was partially enlarged at selected portions, a plurality of holes were provided at the pads and the narrow passageway and enlarged spaces were respectively communicated to the outside through these holes, through which the acid flows.
The replacement principle of the acid fluid in this conventional art utilizes change of dynamic pressure and static pressure which is caused by passing the wakes generated by the travel of the thin plate through the narrow passageways and wide spaces in alternation.
However, there was a problem that when the wide spaces were simply provided in the passageway, the conversion efficiency from dynamic pressure to static pressure was low and it was difficult to drain the wakes flowing along the thin plate with a full utilization of the dynamic pressure of the wakes.
Further, in JP-A-57-41384 (1982) reciprocatingly movable frames are provided so as to sandwich a thin plate at the top and bottom thereof, and on the planes of the movable frames facing to the thin plate a large number of stirring protrusions are provided. When the frames are moved reciprocatingly, the acid fluid covering the surfaces of the thin plate is stirred and disturbed by the protrusions which reciprocate together with the movable frames, thereby, the layer of the acid fluid traveling with the thin plate is broken, and the acid fluid is replaced.
However, in the device disclosed in JP-A-57-41384 (1982), there is a problem that although the acid fluid layers moving with the thin plate are stirred by the reciprocation of the stirring protrusions, no positive replacement of the acid fluid in the passageway between the top and bottom movable frames with acid fluid outside the passageway is performed, so that replacement by fresh acid fluid outside the passageway through stirring cannot be expected.